SHIRAI Hisato Solar-Terrestrial Environment Laboratory, Nagoya University, research associate, 太陽地球環境研究所, 助手 (00310996)
KAMIDE Yohsuke Solar-Terrestrial Environment Laboratory, Nagoya University, professor, 太陽地球環境研究所, 教授 (60113099)
|Budget Amount *help
¥2,700,000 (Direct Cost : ¥2,700,000)
Fiscal Year 2000 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 1999 : ¥1,000,000 (Direct Cost : ¥1,000,000)
Fiscal Year 1998 : ¥1,100,000 (Direct Cost : ¥1,100,000)
Energy, momentum, and particles are transported from solar wind into the earth's magnetosphere. This causes global and local changes to high energy particles in the magnetosphere. In this study, we tried to understand the acceleration and disappearance mechanism of high energy particles in the inner magnetosphere, analyzing ground-based and satellite data. Also, we studied the origin of high energy particles in the solar wind.
(1) In order to understand why the number of high energy particles decease in the inner magnetosphere during the storm time, we statistically studied sudden increase (burst) of precipitating electrons, using 1-MeV electron data taken with the SAMPEX satellite. This phenomenon is observed without any dependence on the local time and the magnetic activity level, but its temporal behavior depends on both parameters. Especially in the morning sector, it was found that bursts with a very fast (<1 sec) variation, i.e., micro-bursts, occur. The characteristics of these micro-bursts suggest that electron precipitation is enhanced by an interaction with chorus wave, accompanying substorms during the recovery phase of magnetic storm.
(2) We analyzed two X-class solar flares that occurred on 18 August 1998. It was found that the hard X-ray spectrum of footpoint sources, seems a single power-law shape in the energy range from 14 to 93 keV.This means that footpoint sources are originated by non-thermal electrons. On the other hand, the hard X-ray spectrum of the above-the-looptop source is softer than that of footpoint sources, and it becomes steeper in the energy range above about 50 keV.These results give us a key to solve the question, where electrons, precipitating to footpoints, are accelerated in solar flares.